Chinese fungal study expands the phylogenetically defined Tiliae group and identifies four new Inocybe species

A combined morphological and three-locus molecular study of Inocybe section Marginatae identified four new species in China, documented three additional taxa in the country and proposed a broader phylogenetic definition of the Tiliae group. The research combined observations of newly collected mushrooms with maximum-likelihood and Bayesian analyses of the ITS, LSU and rpb2 loci, expanding the recognized diversity of a group previously characterized mainly through European material.

Basidiomata were collected in Jilin, Qinghai, Shanghai, Zhejiang, Jiangsu and Yunnan. Field documentation covered macroscopic characters, vegetation, substrate, associated plants, geographic coordinates and elevation. Fresh specimens were examined microscopically for spores, basidia, cheilocystidia, pleurocystidia, caulocystidia and the pileipellis and stipitipellis. The final dataset contained 86 samples and a concatenated alignment of 2,691 base pairs, comprising 727 base pairs of ITS, 680 of rpb2 and 1,284 of LSU.

Maximum-likelihood inference used IQ-TREE with 1,000 ultrafast bootstrap replicates, while Bayesian inference used MrBayes. The two analyses produced largely congruent trees. The nodulose-spored ingroup was resolved into seven major clades: the Tabacina, Praetervisae and Oblectabilis groups, section Albodiscae, the Asterospora and Lineata clades, and the expanded Tiliae assemblage. Relationships among several of these lineages remained unresolved, however, rather than forming a single uniformly supported arrangement across the broader nodulose-spored complex.

Each putative new species was recovered as a distinct, fully supported lineage. Inocybe xihuensis was associated with a clade containing I. tiliae, I. tenuiorparietalis, the I. pallida/I. nobilis complex, I. sepiana and I. robertii, but that relationship had limited support, with a bootstrap value of 67% and no reported Bayesian posterior probability. Inocybe zijinshanensis and I. qiongzhuensis formed a strongly supported sister pair, with a posterior probability of 1.00 and bootstrap value of 100%, consistent with their similar basidiomata and pigmentation.

The new species, the former core Tiliae lineage, I. ravida and the Dunensis clade formed a fully supported major clade containing 10 species. The four new taxa were distinguished by combinations of macroscopic and microscopic characters. Inocybe qiongzhuensis has a grayish-brown pileus, a pink-tinged pruinose stipe, nodulose spores and long subutriform hymenial cystidia whose walls thicken toward the apex. Inocybe ravida has an earthy-yellow to ginger-yellow pileus, an entirely pruinose stipe, spores with 7–11 small nodules and smaller fusiform hymenial cystidia.

Inocybe zijinshanensis has appressed pale-brown squamules, a pale flesh-pink stipe, spores bearing 7–11 small nodules and broadly fusiform hymenial cystidia. Inocybe xihuensis has a yellowish-brown pileus with a dark center, granular stipe pruina, spores with 9–13 small rounded nodules and obtusely fusiform to fusiform hymenial cystidia. The four species were collected in subtropical evergreen broad-leaved forests dominated by Fagaceae, with the new taxa known from Yunnan, Zhejiang, Jiangsu and Shanghai.

The study also confirmed Chinese occurrences of I. tiliae, the I. pallida/I. nobilis complex and I. dunensis. Seven collections from poplar plantations in northeastern China clustered strongly with European I. tiliae, with a posterior probability of 1.00 and bootstrap value of 90%. The Chinese collections showed morphological variation and some genetic differentiation, but support for differentiation was limited, so the authors treated them as conspecific with I. tiliae. A Qinghai specimen was placed within the I. pallida/I. nobilis complex, while specimens from Jilin and Xizang formed a strongly supported clade with European I. dunensis.

Based on the phylogenetic results, the authors broadened the Tiliae group to include the major clade, the Pseudohiulca clade and the Velata clade. The resulting group contains 12 species and two species complexes. Its defining combination includes robust basidiomata, yellowish-ochraceous to dark-brown pilei, often pink-tinged stipes, bulbous or marginate stipe bases, stipe pruina extending over the upper portion at least, and often a spermatic odor. Two previously emphasized characteristics proved less consistent at the group level: stipe pruina was reduced in the Velata clade, and average spore length exceeded 10 μm in most, but not all, members.

Several limitations constrain the findings. The Chinese I. pallida/I. nobilis complex was represented by one collection, and a single overmature Gansu specimen was used to assess a lineage sister to I. velata. DNA could not be obtained from the preserved type material of I. pallida or I. nobilis, and no stable diagnostic characters separated the two names, so they were retained provisionally as a species complex. The broader relationships among several nodulose-spored lineages also remained unresolved. Within these boundaries, the study documents substantial previously undocumented diversity of the Tiliae group in China and shows that the known Chinese diversity of Inocybe remains insufficiently characterized.

Subject of Research: Phylogenetic delimitation and Chinese diversity of the Inocybe Tiliae group

Article Title: Molecular phylogeny of the Tiliae group ( Inocybe sect. Marginatae ) and delimitation of the group with new discoveries

Article References: Fan, Y.-G., Xu, Y.-R., Li, Y., Chang, C., Deng, L.-S., & Yu, W.-J. (2026). Molecular phylogeny of the Tiliae group (Inocybe sect. Marginatae) and delimitation of the group with new discoveries. MycoKeys, 139, 109-138. https://doi.org/10.3897/mycokeys.139.204873

Image Credits: AI Generated

DOI: 10.3897/mycokeys.139.204873

Keywords: Inocybe, Tiliae group, fungal phylogeny, new species, China, ITS, LSU, rpb2, morphology, fungal diversity, Molecular, phylogeny